1. Field of the Invention
The present invention relates to a laminated iron core of a stator or a rotor which forms an electric motor and a manufacturing method for the laminated iron core.
2. Description of the Related Art
An iron core (a laminated iron core) of a stator or a rotor which forms an electric motor is manufactured in such a manner that, for instance, a press line 80 shown in FIG. 7 is used to blank or stamp out a thin electromagnetic steel plate (a sheet material) 81 to form a prescribed configuration, and the prescribed number of blanked or stamped iron core pieces are laminated and interlocked together by a caulking or welding unit. FIG. 7 indicates an un-coiler 82 which rewinds the electromagnetic steel plate 81, a sensor 83 which detects a looseness of the rewound electromagnetic steel plate 81, a leveler 84 which removes a distortion of the electromagnetic steel plate 81, and a press 85 provided with a progressive feed die 86 which blanks or stamps the iron core piece.
Here, as shown in FIG. 8A, when a caulking part is used as a interlocking unit of the laminated iron core pieces 87, a depth of the caulking part is an important manufacturing condition in order to obtain a prescribed interlocking force.
In recent years, iron cores which use a thinner electromagnetic steel plate increase in order to improve a performance of the electric motor. However, since as the thickness of the electromagnetic steel plate is smaller, the number of blanked iron core pieces is the more increased to laminate the iron core pieces in a prescribed thickness. Accordingly, when the usual manufacturing method is used that the iron core pieces are blanked or stamped one piece by one piece, as the thickness of the electromagnetic steel plate is more decreased, the productivity of the iron core pieces is the more deteriorated.
As a countermeasure thereof, there is a method that a plurality of electromagnetic steel plates is piled and the piled electromagnetic steel plates are blanked or stamped at the same time. Thus, the productivity is increased integer times as large as that when the iron core pieces are blanked or stamped out one piece by one piece (for instance, two times when the two electromagnetic steel plates are piled), so that the productivity can be prevented from being deteriorated due to the reduced thickness of the plate (for instance, see JP-A-2003-219585).